1. Field of the Invention
This invention relates to a data transmitting method, a data recording apparatus, a data record medium(recording, recordable or recorded) and a data reproducing apparatus, which may be applied to prevention of duplication or unauthorized use of transmitted or recorded/reproduced digital data.
2. Description of Related Art
Recently, with increased capacity and coming into widespread use of digital recording media, such as optical discs, prohibition of duplication or unauthorized use thereof has become incumbent. That is, digital audio data or digital video data can be duplicated by copying or dubbing without deterioration, while computer data can be duplicated to give data which are the same as the original data, so that troubles are caused due to unauthorized duplication.
For evading unauthorized duplication of digital audio data or digital video data, the standards for so-called serial copying management system (SCMS) or the copying generation management system (CGMS) have so far been known. However, since these standards set a copying inhibiting flag at a specified portion of recording data, data may be extracted by whole copying, that is so-called dump copying, of digital bi-level signals.
There is shown of JP Patent Kokai Publication JP-A-7-182766 (1995) a method consisting in recording non-duplicatable information (confidential information) on a record medium and using this information for prohibiting unauthorized copying. However, this method is not immune from the above problem of data extraction by dump copying.
In particular, the whole copying or dump copying is carried out by a technique of directly extracting digital bi-level signals read out by a reproducing head, such as an optical head, thus causing troubles.
The same may be said of the currently developed digital video disc (DVD), such that, in a replay-only disc that may be duplicated in large quantities, some measures must be taken in connection with formatting.